The invention relates to a transfer arrangement, particularly for a transfer press and to a method for transporting workpieces by means of a transfer arrangement including a guide track on which a carriage is movably supported.
The transport of workpieces between individual presses has been mechanized for some time in connection with different press installations, workpiece conveyor lines from press-to-press and similar devices. Particularly for presses arranged closely adjacent one another and for the handling of smaller sheet metal parts, so-called gripper track transfer equipment has been used as shown for example in DE 43 10 057 A1. With this kind of equipment, the workpieces are transferred by means of two parallel gripper rails which are moved in the rhythm of the presses so that one is moved toward and below the workpiece on other gripper rails and then raised to support the workpiece and then, with the workpiece supported thereon is moved away from the other gripper rails, and then again downwardly to deposit the workpiece on another set of rails or other support device. During the press stroke, the gripper rails are again returned to the start-out position.
The transport of larger sheet metal parts is facilitated by the so-called suction transfer devices as they are described in DE 195 06 518 A1. They include suction bridges which are arranged transverse to the transport direction and are supported at their two ends by carriages disposed on guide rails. Raising and lowering of the guide rails results in raising and lowering the suction bridges and consequently the workpieces. For moving the suction bridges, so-called push rods are provided on the guide rails which are operated by electric motors.
For individual presses which are to be interlinked and which are set up at a certain distance from each other, transfer arrangements are known which operate individually between two press stages. DE 195 21 976 A1, for example, discloses in one of the shown embodiments a transfer arrangement which includes a vertically adjustable carriage. The carriage is provided with a parallelogram-arm structure at the lower end of which a two-element pivot arm is arranged. The pivot arm may have vertical or horizontal pivot joint axes. In the arrangement with a horizontal pivot axis, the parallelogram arm structure operates like a pendulum. The arm can be extended in one direction toward an upstream workpiece or in another direction toward a downstream workpiece. The joints pivot in the process about a horizontal axis.
With such a drive arrangement, large distances between presses can be bridges and the transfer of the workpieces can be arranged to be reasonably flexible. For example, the distances between the presses of a transfer set up do not need to be uniform.
The height required for the pivot movement is substantial. This means that the tools must be opened wide to permit the pivot movement of the arms. To overcome this disadvantage arms with vertical pivot axes are disclosed in the same reference. Such arrangements however, with long arms, suffer from bearing inaccuracies resulting in inaccurate positioning of the workpieces.
Furthermore, the power required for the transport of the workpieces and the movement of the arms and the engagement structures must be provided by pivot drives which require high torques. If the drives are positioned at the various joints of the arms, these drives must be relatively large in order to generate the required torques and they too must be moved.
It is therefore the object of the present invention to provide an improved transfer arrangement and method of operating such a transfer arrangement.